Metropolitan regions - innovation, competition, capacity for action: Findings of the joint working group Academy for Spatial Research and Planning (ARL, Hanover), German Institute of Urban Affairs (difu, Berlin), Research Institute for Regional and Urban Development, Building and Construction of the Federal State of North Rhine-Westphalia (ILS NRW, Dortmund), Leibniz Institute for Regional Development and Structural Planning (IRS, Erkner)